a flood of light over the subject, and called forth feelings of peculiar
satisfaction, and of gratefulness to Mr. Darwin, which still come up afresh
whenever the subject of coral islands is mentioned. The Gambier Islands in
the Paumotus, which gave him the key to the theory, I had not seen; but on
reaching the Feejees, six months later, in 1840, I found there similar
facts on a still grander scale and of a more diversified character, so that
I was afterward enabled to speak of his theory as established with more
positiveness than he himself, in his philosophic caution, had been ready to
adopt. His work on coral-reefs appeared in 1842, when my report on the
subject was already in manuscript. It showed that the conclusions on other
points, which we had independently reached, were for the most part the
same. The principal points of difference relate to the reason for the
absence of corals from some coasts, and the evidence therefrom as to
changes of level, and the distribution of the oceanic regions of elevation
and subsidence--topics which a wide range of travel over the Pacific
brought directly and constantly to my attention."

Among the Reports of the United States Exploring Expedition, two important
works from the pen of Professor Dana made their appearance;--one on
"Zoophytes," which treats at length on "Corals and Coral-Animals," and the
other on "Coral-Reefs and Islands." In 1872, Dana prepared a work of a
more popular character in which some of the chief results of his studies
are described; it bore the title of "Corals and Coral-Islands." Of this
work, new and enlarged editions appeared in 1874 and 1890 in America, while
two editions were published in this country in 1872 and 1875. In all these
works their author, while maintaining an independent judgment on certain
matters of detail, warmly defends the views of Darwin on all points
essential to the theory.

Another able exponent and illustrator of the theory of coral-reefs was